The antenna effect, also called plasma induced gate oxide damage, is an effect that can potentially cause yield and reliability problems during the manufacture of metal-oxide-semiconductor (MOS) integrated circuits. Damage is caused by the accumulation of charges collected by floating conductors which act like antennas by focusing energy into a transistor during a plasma process. Specifically, charging may occur during intermediate steps of the manufacturing process when uncovered conductive elements are directly exposed to plasma. When the conductive elements are connected to a gate of a transistor, the plasma-induced charge that has accumulated on the conductive elements can discharge through the gate oxide of the transistor causing damage to the transistor. Plasma induced gate oxide damage can occur during both front and back end of line processes and, thus, is a type of inline charging damage.
Integrated circuit manufacturers commonly impose antenna rules that are designed to avoid plasma induced gate oxide damage. Antenna rules may include: limiting the size of large plates of metal or polysilicon connected to gate of a transistor; restricting a maximum antenna size or antenna ratio for a circuit layout; and thereby limiting the total charge accumulated on metal connected to a gate to less than a threshold amount. Conventional antenna rules ignore transistors in which there is a shunt path between the gate and the source/drain of the transistor. These shunted transistors are considered immune to plasma induced gate oxide damage due to the conductive shunt path. However, treating such transistors as immune disadvantageously fails to take into account the resistance of the shunt path.